CN114910541A - Electrochemical sensor, preparation method and application thereof - Google Patents

Abstract

The invention discloses an electrochemical sensor and its preparation method and application. The electrochemical sensor of the present invention comprises: a carbon-containing non-conductive substrate and a three-electrode system arranged in a groove on the surface of the carbon-containing non-conductive substrate; the three-electrode system is composed of Ag/AgCl/carbon electrode, Pt/carbon electrode and graphdiyne/ Copper/carbon electrode composition. The preparation method of the electrochemical sensor of the present invention comprises the following steps: etching three electrode slots containing a conductive carbon layer on the surface of a carbon-containing non-conductive substrate with a laser, and then depositing copper nanoparticles in one electrode slot After in situ growth of graphdiyne, Ag/AgCl slurry was coated in one electrode slot, and platinum nanoparticles were deposited in one electrode slot. The electrochemical sensor of the present invention is an integral material containing a three-electrode system, which not only has the advantages of convenient portability, simple preparation and low cost, but also can accurately and efficiently detect the tryptophan content of unknown solutions or plants themselves.

Description

Electrochemical sensor, preparation method and application thereof

technical field

The invention relates to the technical field of electrochemical sensors, in particular to an electrochemical sensor and a preparation method and application thereof.

Background technique

Electrochemical sensors have very important practical value in environmental monitoring, food inspection, drug analysis and plant active molecule analysis. With the continuous progress of current electrochemical sensing technology, the requirements for electrochemical sensing are also gradually increasing. It is particularly important to develop new simple, sensitive, durable, accurate and reliable electrochemical sensors. Compared with traditional electrode systems, electrochemical chip electrodes have the advantages of simple fabrication, low cost, wide application range, and high integration, and can be used as portable sensors.

Tryptophan is an important precursor for auxin biosynthesis in plants, and its structure is similar to indoleacetic acid (IAA), which is ubiquitous in higher plants. In plants, tryptophan, as a synthetic precursor, is first decarboxylated to form tryptamine, then oxidatively deaminated to form indoleacetaldehyde, and finally into indoleacetic acid. Auxin regulates a large number of life processes in the process of plant growth and development, so it is of great significance to develop a method that can directly monitor the content of tryptophan in the plant itself. At present, researchers have constructed a composite film type electrochemical sensor by modifying the electrode surface with Au-Ag nanoparticles and polydimethyldiallylammonium chloride modified graphene oxide, but the cost is relatively high. High, large volume, high detection limit for detecting tryptophan, complicated use and other technical problems.

Therefore, it is urgent to research and develop an electrochemical sensor that not only has the advantages of portability, simple preparation and low cost, but also can accurately and efficiently detect the content of tryptophan.

SUMMARY OF THE INVENTION

In order to overcome the problems existing in the prior art, one of the objectives of the present invention is to provide an electrochemical sensor.

Another object of the present invention is to provide a method for preparing the above electrochemical sensor.

The third object of the present invention is to provide the application of the above electrochemical sensor.

The inventive concept of the present invention is as follows: first, carbonize the surface of the carbon-containing non-conductive base material by laser etching technology to obtain three electrode slots containing conductive carbon layers; Copper nanoparticles (referred to as Cu NPs) were loaded on the grooves by electrodeposition, and then graphdiyne (GDY) was loaded by in-situ synthesis to obtain graphdiyne/copper nanoparticles/carbon electrodes (ie GDY/GDY). Cu NPs/carbon electrode); on an electrode slot containing a conductive carbon layer, the Ag/AgCl composite material was supported by coating method to obtain an Ag/AgCl/carbon electrode; in an electrode slot containing a conductive carbon layer The platinum nanoparticles (referred to as Pt NPs) are supported by electrodeposition to obtain platinum nanoparticles/carbon electrodes (ie, Pt NPs/carbon electrodes); finally, an electrochemical sensor is obtained. At the same time, the schematic structural diagram of the electrochemical sensor of the present invention is shown in Figure 1. It uses GDY/Cu NPs/carbon electrode as the working electrode, Ag/AgCl/carbon electrode as the reference electrode, and Pt NPs/carbon electrode as the reference electrode. Electrode. The electrochemical sensor prepared by this method is an integral material and also a chip electrode. It can not only be used as an electrochemical sensor for the detection of tryptophan in unknown solutions and the real-time monitoring of the tryptophan content of plants, but also has the advantages of strong controllability, low cost, small size, wide application range, fast reaction speed, and high detection rate. Low limit and other advantages.

In order to achieve the above object, the technical scheme adopted by the present invention is:

In a first aspect, the present invention provides an electrochemical sensor, which comprises a carbon-containing non-conductive substrate and a three-electrode system disposed in a groove on the surface of the carbon-containing non-conductive substrate; the three-electrode system is composed of Ag/AgCl/carbon. electrode, Pt/carbon electrode and graphdiyne/copper/carbon electrode; the Ag/AgCl/carbon electrode includes a carbon layer and an Ag/AgCl layer; the Pt/carbon electrode includes a carbon layer and platinum nanoparticles layer; the composition of the graphdiyne/copper/carbon electrode includes a carbon layer and a copper nanoparticle-graphdiyne composite layer.

Preferably, the carbon-containing non-conductive substrate is one of polystyrene substrate, polyimide substrate, wood substrate, and polytetrafluoroethylene substrate.

In a second aspect, the present invention provides a method for preparing the above electrochemical sensor, comprising the following steps:

Three electrode slots A, B and C containing conductive carbon layers are etched on the surface of the carbon-containing non-conductive substrate by laser etching, and then copper nanoparticles are deposited in the electrode slot A to grow graphdiyne in situ. Ag/AgCl slurry is coated in position B, and platinum nanoparticles are deposited in electrode groove C to obtain an electrochemical sensor.

Preferably, the laser etching is performed under the conditions of a scan rate of 30mV/s to 100mV/s and a current of 12A to 25A.

Preferably, the shape of the electrode slot containing the conductive carbon layer is one of a square, a rectangle, a circle, and an ellipse.

Preferably, the spacing between the electrode slots containing the conductive carbon layer is 3 mm to 10 mm.

Preferably, the deposition of the electrode slot A is potentiostatic deposition, the deposition voltage is -1.0V to -0.5V, and the deposition time is 50s to 200s.

Preferably, the electrolyte used in the potentiostatic deposition is a soluble copper salt solution.

Preferably, the concentration of the soluble copper salt solution is 0.1 mol/L to 1.0 mol/L.

Preferably, the soluble copper salt solution is one or more of copper sulfate, copper nitrate and copper chloride.

Specifically, the potentiostatic deposition on the electrode slot A is to first clean and dry the monolithic material containing conductive carbon, and then immerse it in a soluble copper salt solution. The electrode slot A containing the conductive carbon layer is The working electrode takes the existing Ag/AgCl electrode (not the electrode on the sensor) as the reference electrode and the existing platinum disk electrode as the counter electrode, and sets the relevant constant potential deposition parameters, so as to realize the The effect of nanoparticle copper loaded on the electrode slots of the conductive carbon layer.

Preferably, the specific operation of the in-situ growth of graphdiyne is to place the carbon-containing non-conductive substrate after depositing copper nanoparticles in a graphdiyne precursor solution, and treat it at a temperature of 60°C to 100°C for 12h～ 72h.

Preferably, the specific operation of growing graphdiyne in situ is performed under a protective atmosphere.

Preferably, the protective atmosphere is one or more of nitrogen, helium and argon.

Preferably, the composition of the graphdiyne precursor solution includes: hexa(ethynyl)benzene and an organic solvent.

Preferably, the preparation method of hexa(ethynyl)benzene includes the following steps: placing the hexa(trimethylsilylethynyl)benzene solution in a nitrogen atmosphere and stirring at 0°C to obtain hexa(ethynyl)benzene .

Preferably, the concentration of the hexa(trimethylsilylethynyl)benzene solution is 0.01g/L～0.5g/L.

Further preferably, the concentration of the hexa(trimethylsilylethynyl)benzene solution is 0.1 g/L.

Preferably, the organic solvent is one or more of acetonitrile, tetrahydrofuran and pyridine.

Further preferably, the solvents in the graphdiyne precursor solution are acetonitrile, pyridine and tetrahydrofuran, and the volume ratio of pyridine to acetonitrile is 6:3 to 6:7.

Preferably, the specific operation process of the in-situ growth of graphdiyne does not include stirring.

Preferably, the preparation method of the electrochemical sensor further includes the steps of washing and drying.

Preferably, the cleaning agent used in the cleaning is one or more of water, toluene, acetone, and ether.

Preferably, the specific drying operation is infrared drying or vacuum drying.

Preferably, the mass fraction of Ag in the Ag/AgCl slurry is 60%-90%.

Preferably, the deposition of the electrode slot C is potentiostatic deposition, the deposition voltage is -0.7V to -0.1V, and the deposition time is 50s to 200s.

Specifically, the potentiostatic deposition on the electrode slot C is based on the electrode slot C containing the conductive carbon layer as the working electrode, and the existing Ag/AgCl electrode (not the electrode on the sensor) as the reference electrode. , using the existing platinum disk electrode as the counter electrode.

In a third aspect, the present invention provides the application of the above electrochemical sensor in tryptophan detection.

In a fourth aspect, the present invention provides an application of the above electrochemical sensor for real-time monitoring of changes in tryptophan content in plants.

Preferably, the method for monitoring the change of tryptophan content in the plant body in real time comprises the following steps:

1) In the tryptophan-electrolyte system with different concentrations, three electrodes were formed by using graphyne/copper/carbon electrode as working electrode, Pt/carbon electrode as counter electrode, and Ag/AgCl/carbon electrode as reference electrode system, using differential pulse voltammetry to detect different concentrations of tryptophan-phosphate buffer solution system, and obtain the standard curve of current response value-concentration;

2) Measure the current response value of the sample by pulse voltammetry, and then compare it with the standard curve to obtain the real-time tryptophan content in the plant.

Specifically, the current response value in the standard curve of current response value-concentration is the maximum current response value measured by differential pulse voltammetry.

Preferably, the test parameters in the differential pulse voltammetry are: enrichment potential -0.5-0.5V, enrichment time 15s-300s, resting time 10s-15s, and the voltage test interval is 0.2V-1.2V.

Preferably, the pH value of the tryptophan-phosphate buffer solution in step 1) is 5.0-7.0.

Preferably, the sample in step 2) is a tryptophan-containing solution or a fruit of a plant.

The beneficial effects of the present invention are: the electrochemical sensor of the present invention is an integral material with a three-electrode system, which not only has the advantages of convenient portability, simple preparation and low cost, but also can accurately and efficiently detect unknown solutions or plants. its own tryptophan content. Specifically:

(1) The electrochemical sensor of the present invention is an integral material, which has the characteristics of being convenient to carry and easy to use;

(2) The electrochemical sensor of the present invention has the advantages of simple manufacture, low cost, wide application range, high integration, fast response speed, low detection limit (0.039 μM), and the like;

(3) The present invention obtains a working electrode modified with copper nanoparticles-graphyne composite material by in-situ synthesis of graphdiyne method, and the electrode is a kind of working electrode with good load fastness, large specific surface area, many tryptophan adsorption sites, Chip electrode material with strong conductivity;

(4) The preparation method of the electrochemical sensor in the present invention is controllable and can control the content of copper nanoparticles and graphdiyne on the working electrode, so as to increase the adsorption tryptophan site, so that the tryptophan adsorption can be realized. The detection sensitivity is high and the technical effect of real-time detection of tryptophan content changes in plants is suitable for practical application and promotion.

Description of drawings

FIG. 1 is a schematic diagram of the electrochemical sensors in Examples 1-4.

FIG. 2 is a SEM image of the working electrode on the electrochemical sensor in Example 2. FIG.

FIG. 3 is a graph of the current-voltage curve measured by differential pulse voltammetry of tryptophan solutions of different concentrations in Example 3. FIG.

FIG. 4 is a standard curve diagram of current response value-concentration in Example 3. FIG.

FIG. 5 is a graph of the current-voltage curve measured by differential pulse voltammetry in Example 4. FIG.

FIG. 6 is a schematic diagram of the tryptophan detection method for plant material in Example 4. FIG.

Detailed ways

The content of the present invention will be further described in detail below through specific embodiments.

The present invention provides an electrochemical sensor, the schematic diagram of its structure and composition, as shown in FIG. 1 .

As can be seen from FIG. 1: the present invention is to first carry out carbonization treatment on the surface of the carbon-containing non-conductive base material by laser etching technology to obtain three electrode slots containing conductive carbon layers; Copper nanoparticles were loaded on the electrode slot by electrodeposition, and graphdiyne (GDY) was loaded by in-situ synthesis method; Ag/GDY was loaded on the second electrode slot containing conductive carbon layer by coating method. AgCl composite material; platinum nanoparticles are loaded on the third electrode slot containing a conductive carbon layer by electrodeposition to obtain a graphdiyne-modified electrochemical sensor. The graphdiyne-modified electrochemical sensor uses the electrode slot containing the conductive carbon layer loaded with copper nanoparticles and graphdiyne (i.e. GDY/Cu NPs/carbon electrode) as the working electrode, and the electrode slot loaded with Ag/AgCl composite material is used as the working electrode. The electrode slot of the conductive carbon layer (ie, Ag/AgCl/carbon electrode) was used as the reference electrode, and the electrode slot of the conductive carbon layer loaded with platinum nanoparticles (ie, Pt NPs/carbon electrode) was used as the counter electrode.

Example 1

This embodiment provides an electrochemical sensor, which comprises: a base material and three electrode slots containing conductive carbon layers on the surface of the base material; wherein one electrode slot containing a conductive carbon layer is loaded with silver and silver chloride, one electrode slot containing a conductive carbon layer is loaded with platinum nanoparticles, and one electrode slot containing a conductive carbon layer is loaded with graphdiyne and copper nanoparticles.

A preparation method of an electrochemical sensor, comprising the following steps:

1) On the polystyrene film (the size of the polystyrene film is: 4.5×3.5×0.12cm), 3 electrode slots containing conductive carbon layers are etched by laser, and the electrode slots to be processed are set to 4cm×5mm The distance between the electrode slots containing the conductive carbon layer is set to 5mm, and the process parameters of the laser etching are set to: scan speed 60mV/s, current 18A, to obtain a monolithic material containing conductive carbon;

2) Rinse the monolithic material containing conductive carbon in step 1) with ultrapure water, dry it with an infrared lamp, and then immerse it in a 0.5mol/L copper sulfate solution, set its deposition voltage to -0.6V, and deposit at a constant potential. The time is 50s, and copper nanoparticles are deposited on the working electrode slot by the potentiostatic method to obtain a monolithic material containing copper and conductive carbon;

3) 60 mL of pyridine was mixed with 40 mL of acetonitrile, placed in a round-bottomed flask together with the monolithic material containing copper and conductive carbon, and 5 mL of hexa(ethynyl)benzene solution was mixed with 45 mL of tetrahydrofuran to obtain hexa(ethynyl)benzene- The tetrahydrofuran mixed solution was put into a dropping funnel, assembled with a round-bottomed flask, checked for air tightness, passed nitrogen for 20 minutes, then opened the dropping valve, controlled the flow rate, and finished dropping the hexa(ethynyl)benzene-tetrahydrofuran mixed solution in 5 hours, Then heated to 70°C, maintained for 72h, after natural cooling to room temperature, washed with hot toluene, acetone, and ether to obtain a monolithic material containing graphdiyne/copper nanoparticles/carbon electrode (working electrode);

4) Coat Ag/AgCl slurry on the reference electrode slot, the mass fraction of Ag in the slurry accounts for 70%, and use constant potential electrodeposition to deposit platinum nanoparticles in the counter electrode slot, and set the deposition voltage to -0.7 V, the deposition time is 100s, and the electrochemical sensor is obtained by cleaning and drying;

Wherein, in step 2), the working electrode slot in the monolithic material containing conductive carbon is used as the working electrode, another Ag/AgCl electrode is used as the reference electrode, and another platinum disk electrode is used as the counter electrode to conduct electrical Deposit copper nanoparticles.

The 0.1 g/L hexa(ethynyl)benzene solution in this example was obtained by stirring 10 mL of a 0.1 g/L hexa(trimethylsilylethynyl) benzene solution for 20 min under the condition of The g/L hexa(trimethylsilylethynyl)benzene solution is prepared by using hexa(trimethylsilylethynyl)benzene as a solute and tetrahydrofuran as a solvent.

Example 2

A preparation method of an electrochemical sensor, comprising the following steps:

1) On the polystyrene film (the size of the polystyrene film is: 5.6×5.0×0.12cm), 3 electrode slots containing conductive carbon layers are etched by laser, and the electrode slots to be processed are set to 4.5cm× 8mm rectangle, the spacing between the electrode slots containing the conductive carbon layer is set to 8mm, and the process parameters of the laser etching are set to: scan speed 80mV/s, current 20A, to obtain a monolithic material containing conductive carbon;

2) Rinse the monolithic material containing conductive carbon in step 1) with ultrapure water, dry it with an infrared lamp, and then immerse it in a 0.5mol/L copper sulfate solution, set its deposition voltage to -0.6V, and deposit at a constant potential. The time is 100s, and copper nanoparticles are deposited on the working electrode slot by the potentiostatic method to obtain a monolithic material containing copper and conductive carbon;

3) 90 mL of pyridine was mixed with 75 mL of acetonitrile, then placed in a round-bottomed flask with the monolithic material containing copper and conductive carbon, and 5 mL of 0.1 g/L hexa(ethynyl)benzene solution was mixed with 60 mL of tetrahydrofuran to obtain hexa(ethynyl) Ethynyl)benzene-tetrahydrofuran mixed solution was put into a dropping funnel, assembled with a round-bottomed flask, checked for air tightness, passed nitrogen for 20 minutes, then opened the drip valve, controlled the flow rate, and finished dropping the hexa(ethynyl)benzene in 5h -The mixed solution of tetrahydrofuran is then heated to 80°C and maintained for 48h. After being naturally cooled to room temperature, it is washed with hot toluene, acetone and ether to obtain a monolithic material containing graphdiyne/copper nanoparticles/carbon electrode (working electrode);

4) Coat the Ag/AgCl slurry on the reference electrode slot, the mass fraction of Ag in the slurry accounts for 85%, and electrodeposit platinum nanoparticles at the counter electrode slot with constant potential, and set the deposition voltage to -0.4 V, the deposition time is 100s, and the electrochemical sensor is obtained by cleaning and drying;

Wherein, in step 2), the working electrode slot in the monolithic material containing conductive carbon is used as the working electrode, another Ag/AgCl electrode is used as the reference electrode, and another platinum disk electrode is used as the counter electrode to conduct electrical Deposit copper nanoparticles.

The 0.1 g/L hexa(ethynyl)benzene solution in this example was obtained by stirring 10 mL of a 0.1 g/L hexa(trimethylsilylethynyl) benzene solution for 20 min under the condition of The g/L hexa(trimethylsilylethynyl)benzene solution is prepared by using hexa(trimethylsilylethynyl)benzene as a solute and tetrahydrofuran as a solvent.

The SEM image of the working electrode in the electrochemical sensor in Example 2 is shown in FIG. 2 .

It can be seen from Figure 2 that graphdiyne is grown on the surface of the working electrode in the electrochemical sensor, which increases the roughness of the surface, thereby effectively increasing the specific surface area and conductivity of the working electrode, providing more adsorption sites for tryptophan. The contact area between the electrode and the electrolyte in the electrochemical process is effectively increased, thereby improving the electrochemical performance of the working electrode.

Example 3

A preparation method of an electrochemical sensor, comprising the following steps:

1) On the polyimide film (the size of the polyimide film is: 5.6×5.0×0.12cm), 3 electrode slots containing conductive carbon layers are etched by laser, and the electrode slot to be processed is set to 4.5 cm×8mm rectangle, the spacing between the electrode slots containing the conductive carbon layer is set to 8mm, and the process parameters of the laser etching are set to: scan speed 64mV/s, current 16A, to obtain a monolithic material containing conductive carbon;

2) Rinse the monolithic material containing conductive carbon in step 1) with ultrapure water, dry it with an infrared lamp, and then immerse it in a 0.5mol/L copper sulfate solution, set its deposition voltage to -0.6V, and deposit at a constant potential. The time is 100s, and copper nanoparticles are deposited on the working electrode slot by the potentiostatic method to obtain a monolithic material containing copper and conductive carbon;

3) Mix 60 mL of pyridine with 45 mL of tetrahydrofuran, place it in a round-bottomed flask with the monolithic material containing copper and conductive carbon, and mix 5 mL of 0.1 g/L hexa(ethynyl) benzene solution with 40 mL of acetonitrile to obtain hexa(ethynyl) benzene. Ethynyl)benzene-acetonitrile mixed solution, put it into a dropping funnel, assemble it with a round-bottomed flask, check the air tightness, pass nitrogen for 20min, then open the dripping valve, control the flow rate, and finish dropping hexa(ethynyl)benzene- The mixed solution of acetonitrile was then heated to 80°C and maintained for 48h. After cooling to room temperature naturally, it was washed with hot toluene, acetone and ether to obtain a monolithic material containing graphyne/copper nanoparticles/carbon electrode (working electrode);

4) Coating Ag/AgCl slurry on the reference electrode slot, the mass fraction of Ag in the slurry accounts for 85%, and electroplating platinum nanoparticles in the counter electrode slot with a constant potential, and setting the deposition voltage to -0.2 V, the deposition time is 100s, and the electrochemical sensor is obtained by cleaning and drying;

Wherein, in step 2), the working electrode slot in the monolithic material containing conductive carbon is used as the working electrode, another Ag/AgCl electrode is used as the reference electrode, and another platinum disk electrode is used as the counter electrode to conduct electrical Deposit copper nanoparticles.

The 0.1 g/L hexa(ethynyl)benzene solution in this example was obtained by stirring 10 mL of a 0.1 g/L hexa(trimethylsilylethynyl) benzene solution for 20 min under the condition of The g/L hexa(trimethylsilylethynyl)benzene solution is prepared by using hexa(trimethylsilylethynyl)benzene as a solute and tetrahydrofuran as a solvent.

A method for a standard curve for tryptophan testing, the steps of which include:

1) Immerse the electrochemical sensor in 10 mL of tryptophan-phosphate buffer system (pH=6.5) with stirring bar concentrations of 10 μM, 20 μM, 30 μM, 40 μM, 50 μM, 70 μM, and 90 μM, and set the electrochemical workstation differential Pulse voltammetry parameters: enrichment potential +0.2V, enrichment time 15s, resting time 10s, voltage interval selection 0.55V-1.0V, differential pulse voltammetry curve measured sequentially;

2) The maximum current response value in the measured differential pulse voltammetry curve corresponds to different concentrations of tryptophan phosphate buffer, and the tryptophan concentration is used as the abscissa, and the maximum current response value is used as the ordinate, and the current is drawn. Standard curve of response value - tryptophan concentration. It should be noted that "μM", that is, "μmol/L", is a unit of solution concentration.

The voltage-current curves measured by differential pulse voltammetry for different concentrations of tryptophan solutions in Example 3 are shown in FIG. 3 . Select the current response value with a voltage value of about 0.696V as the ordinate, and the concentration of the tryptophan solution as the abscissa to make a standard curve of the current response value-tryptophan concentration, as shown in Figure 4.

It can be seen from Fig. 3 and Fig. 4 that as the tryptophan concentration increases, the peak current value corresponding to the differential pulse voltammetry curve also increases. Taking the tryptophan solution concentration as the abscissa, and the peak current of the corresponding differential pulse voltammetry curve as the ordinate, the standard curve for tryptophan test can be obtained, as shown in Figure 4, the correspondence between the peak current value and the concentration The relationship is: i=0.05157C+0.5343, R ² =0.997, where i represents the peak current value of the differential pulse voltammetry curve, C represents the molar concentration of tryptophan in the standard solution, R ² represents the correlation coefficient and its value is greater than 0.99, indicating that its curve has high reliability.

Through data processing, it can be concluded that the detection limit of the electrochemical sensor composed of this electrochemical sensor is 0.039 μM.

Under the same experimental conditions and electrochemical parameters, 50 μM tryptophan was added to the solution to be tested, and the corresponding peak current increase was 2.65 μA. The recovery rate was 102.77%. This indicates that the standard curve for tryptophan measured by this method has high reliability and can be used to determine the concentration or content of tryptophan in unknown solutions.

Based on the above detection results, it can be seen that the electrochemical sensor in Example 3 or the sensor assembled into it can not only realize the rapid detection of tryptophan, but also have the advantages of small size, wide application range, fast response speed, and high detection rate. limited advantages.

Example 4

A preparation method of an electrochemical sensor, comprising the following steps:

1) On the polyimide film (the size of the polyimide film is: 3.5×3.5×0.12cm), 3 electrode slots containing conductive carbon layers are etched by laser, and the electrode slot to be processed is set to 3.0 cm×5mm rectangle, the spacing between the electrode slots containing the conductive carbon layer is set to 5mm, and the process parameters of the laser etching are set to: scan speed 64mV/s, current 16A, to obtain a monolithic material containing conductive carbon;

2) Rinse the monolithic material containing conductive carbon in step 1) with ultrapure water, dry it with an infrared lamp, and then immerse it in a 0.5mol/L copper sulfate solution, set its deposition voltage to 1.0-2.0V, and set a constant potential of 1.0-2.0V. The deposition time is 100s, and copper nanoparticles are deposited on the working electrode slot by the potentiostatic method to obtain a monolithic material containing copper and conductive carbon;

3) Mix 60 mL of pyridine with 45 mL of tetrahydrofuran, place it in a round-bottomed flask with the monolithic material containing copper and conductive carbon, and mix 5 mL of 0.1 g/L hexa(ethynyl) benzene solution with 40 mL of acetonitrile to obtain hexa(ethynyl) benzene. Ethynyl)benzene-acetonitrile mixed solution, put it into a dropping funnel, assemble it with a round-bottomed flask, check the air tightness, pass nitrogen for 20min, then open the dripping valve, control the flow rate, and finish dropping hexa(ethynyl)benzene- The mixed solution of acetonitrile was then heated to 75°C and maintained for 72h. After cooling to room temperature naturally, it was washed with hot toluene, acetone and ether to obtain a monolithic material containing graphyne/copper nanoparticles/carbon electrode (working electrode);

4) Coating Ag/AgCl slurry on the reference electrode slot, the mass fraction of Ag in the slurry accounts for 85%, and electroplating platinum nanoparticles in the counter electrode slot with a constant potential, and setting the deposition voltage to -0.2 V, the deposition time is 100s, and the electrochemical sensor is obtained by cleaning and drying;

Wherein, in step 2), the working electrode slot in the monolithic material containing conductive carbon is used as the working electrode, another Ag/AgCl electrode is used as the reference electrode, and another platinum disk electrode is used as the counter electrode to conduct electrical Deposit copper nanoparticles.

A method for a standard curve for tryptophan testing, the steps of which include:

1) Immerse the electrochemical sensor in 10 mL of tryptophan phosphate buffer (pH=6.5) with stirring bar concentrations of 10 μM, 20 μM, 30 μM, 40 μM, 50 μM, 70 μM, and 90 μM, and set the electrochemical workstation differential pulse voltage. Amperometric parameters: enrichment potential +0.2V, enrichment time 15s, resting time 10s, voltage interval selection 0.55V-1.0V, differential pulse voltammetry curve measured sequentially;

2) The maximum current response value in the measured differential pulse voltammetry curve corresponds to different concentrations of tryptophan phosphate buffer, and the tryptophan concentration is used as the abscissa, and the maximum current response value is used as the ordinate. Standard curve for tryptophan assay.

A kind of tryptophan detection method (referring to Fig. 6) for plant material, comprises the following steps:

1) Attach the prepared electrochemical sensor to the surface-treated cucumber fruit, and set the electrochemical workstation differential pulse voltammetry parameters: enrichment potential +0.2V, enrichment time 15s, resting time 10s, voltage interval selection 0.45 V-1.0V, the current response value measured by the differential pulse voltammetry method is used to obtain the differential pulse voltammetry curve;

2) The tryptophan concentration in the plant material is obtained by calculation.

The differential pulse voltammetry curve obtained by the test in Example 4 is shown in FIG. 5 . The schematic diagram of the tryptophan detection method for plant material in Example 4 is shown in FIG. 6 .

It can be seen from Figure 5 and Figure 6 that for the detection of tryptophan in cucumber fruit, the differential pulse voltammetry curve shows a current signal at the corresponding peak position, indicating that the electrochemical sensor prepared by this method can be used for the detection of tryptophan in cucumber fruit. For the detection of tryptophan in plants, the real-time change of tryptophan content in a certain part of the plant can be judged by the peak current value of the differential pulse voltammetry curve. This shows that the electrochemical sensor can be used for in vivo detection of plants due to its small size and other advantages. It can be used for in vivo detection of tryptophan content in fruits, stems, leaves and other parts of plants, and can monitor the color of the parts in real time. Variation trend of amino acid concentration.

Based on the above detection results, it can be seen that the electrochemical sensor prepared by this method can realize the in vivo detection of plant tryptophan, and has the advantages of small size, wide application range, fast response speed, and low detection limit.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, The simplification should be equivalent replacement manners, which are all included in the protection scope of the present invention.

Claims (10)

1. an electrochemical sensor, it is characterised in that the composition comprises a carbon-containing non-conductive substrate and a three-electrode system arranged in the groove of the carbon-containing non-conductive substrate surface; The three-electrode system is composed of Ag/AgCl/carbon electrode, Pt/carbon electrode and graphdiyne/copper/carbon electrode; the Ag/AgCl/carbon electrode includes a carbon layer and an Ag/AgCl layer; the Pt/carbon electrode includes a carbon layer and a platinum nanoparticle layer; The composition of the graphdiyne/copper/carbon electrode includes a carbon layer and a copper nanoparticle-graphdiyne composite layer. 2 . The electrochemical sensor according to claim 1 , wherein the carbon-containing non-conductive substrate is one of a polystyrene substrate, a polyimide substrate, a wood substrate, and a polytetrafluoroethylene substrate. 3 . 3. the preparation method of the described electrochemical sensor of claim 1 or 2, is characterized in that, comprises the following steps: Three electrode slots A, B and C containing conductive carbon layers are etched on the surface of the carbon-containing non-conductive substrate by laser etching, and then copper nanoparticles are deposited in the electrode slot A to grow graphdiyne in situ. Ag/AgCl slurry is coated in position B, and platinum nanoparticles are deposited in electrode groove C to obtain an electrochemical sensor. 4 . The method for preparing an electrochemical sensor according to claim 3 , wherein the specific operation of the in-situ growth of graphdiyne is to place the carbon-containing non-conductive substrate after depositing copper nanoparticles in a graphdiyne precursor solution. 5 . and treated for 12h-72h at a temperature of 60°C to 100°C; the composition of the graphdiyne precursor solution includes hexa(ethynyl)benzene and an organic solvent. 5 . The method for preparing an electrochemical sensor according to claim 4 , wherein the specific operation of the in-situ growth of graphdiyne is carried out under a protective atmosphere; the protective atmosphere is nitrogen, helium, and argon. 6 . one or more of them. 6. The method for preparing an electrochemical sensor according to claim 3 or 4, wherein the deposition of the electrode slot A is a potentiostatic deposition, the deposition voltage is -1.0V to -0.5V, and the The deposition time is 50s˜200s; the electrolyte used in the constant potential deposition is a soluble copper salt solution. 7 . The method for preparing an electrochemical sensor according to claim 3 , wherein the mass fraction of Ag in the Ag/AgCl slurry is 60% to 90%. 8 . 8 . The preparation method of an electrochemical sensor according to claim 3 or 4 , wherein the deposition of the electrode slot C is a constant potential deposition, and the deposition voltage is -0.7V～-0.1V, and the The deposition time is 50s to 200s. 9. The application of the electrochemical sensor of claim 1 or 2 in the detection of tryptophan. 10. The application of the electrochemical sensor of claim 1 or 2 for real-time monitoring of changes in tryptophan content in plants.

Images